1. Field of the Invention
This invention relates to beam-forming networks used in conjunction with antenna arrays. More specifically, this invention relates to digital beam-forming networks.
While the present invention is described herein with reference to a particular embodiment, it is understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional embodiments within the scope thereof.
2. Description of the Related Art
Prior to advances in digital technology, beam-forming in response to a wavefront incident on a radar or communications antenna array was performed in the analog domain. In analog beam-forming systems, signals are manipulated in radio frequency (RF) microwave networks or at an intermediate frequency (IF) in the receiver. Efficient analog beam-forming schemes utilized a Butler or a Bliss network. While offering improvements over earlier analog beam-formers, the performance of these more efficient analog networks were nonetheless plagued by resistive losses, critical tolerances, and lack of multiplexing capability. In light of these limitations, efforts have been made to develop digital approaches.
In digital beam-forming systems, operations are performed on digitized baseband in-phase (I) and quadrature-phase (Q) signals within special-purpose digital processors in order to form the beams. Certain radar and communications antennas using digital beam-forming techniques require beam-forming networks with a wide dynamic range in order to maintain accuracy in the face of signal clutter or intentional jamming. This minimum dynamic range requirement currently necessitates the utilization of analog-to-digital (A/D) converters typically having at least seven bits of resolution. Moreover, many conventional digital beam-forming systems employ separate A/D converters to process the I and Q signals associated with each element in the receive array.
Such large-scale use of A/D converters increases the power requirements, weight and complexity of the network. For satellite applications, reductions in the magnitude of each of these parameters is tantamount to an optimal design. Hence, a need exists in the art for a digital beam-forming network employing a minimal number of A/D converters, ideally with each converter being of a minimal bit size.